全文获取类型
收费全文 | 476篇 |
免费 | 89篇 |
国内免费 | 2篇 |
专业分类
567篇 |
出版年
2021年 | 4篇 |
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 16篇 |
2017年 | 12篇 |
2016年 | 12篇 |
2015年 | 17篇 |
2014年 | 13篇 |
2013年 | 15篇 |
2012年 | 25篇 |
2011年 | 29篇 |
2010年 | 21篇 |
2009年 | 18篇 |
2008年 | 13篇 |
2007年 | 27篇 |
2006年 | 22篇 |
2005年 | 15篇 |
2004年 | 10篇 |
2003年 | 10篇 |
2002年 | 8篇 |
2001年 | 17篇 |
2000年 | 15篇 |
1999年 | 16篇 |
1998年 | 6篇 |
1997年 | 10篇 |
1996年 | 7篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1993年 | 8篇 |
1992年 | 11篇 |
1991年 | 12篇 |
1990年 | 6篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1982年 | 6篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1975年 | 8篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1972年 | 4篇 |
1971年 | 5篇 |
1970年 | 5篇 |
排序方式: 共有567条查询结果,搜索用时 15 毫秒
31.
Miklós I Mélykúti B Swenson K 《IEEE/ACM transactions on computational biology and bioinformatics / IEEE, ACM》2010,7(4):763-767
Markov chain Monte Carlo has been the standard technique for inferring the posterior distribution of genome rearrangement scenarios under a Bayesian approach. We present here a negative result on the rate of convergence of the generally used Markov chains. We prove that the relaxation time of the Markov chains walking on the optimal reversal sorting scenarios might grow exponentially with the size of the signed permutations, namely, with the number of syntheny blocks. 相似文献
32.
Phylogeny and the prediction of tree functional diversity across novel continental settings 下载免费PDF全文
33.
Jorgensen ND Andresen JM Pitt JE Swenson MA Zoghbi HY Orr HT 《Journal of neurochemistry》2007,102(6):2040-2048
Spinocerebellar ataxia type 1 (SCA1) is an inherited neurodegenerative disorder. The mutation causing SCA1 is an expansion in the polyglutamine tract of the ATXN1 protein. Previous work demonstrated that phosphorylation of mutant ATXN1 at serine 776 (S776), a putative Akt phosphorylation site, is critical for pathogenesis. To examine this pathway further, we utilized a cell-transfection system that allowed the targeting of Akt to either the cytoplasm or the nucleus. In contrast to HeLa cells, we found that Akt targeted to the cytoplasm increased the degradation of ATXN1 in Chinese hamster ovary cells. However, Akt targeted to the cytoplasm failed to destabilize ATXN1 if Hsp70/Hsc70 was present. Thus, Hsp70/Hsc70 can regulate ATXN1 levels in concert with phosphorylation of ATXN1 at S776. 相似文献
34.
35.
We point out the advantages of membrane inlet mass spectrometry for the measurement of nitric oxide in aqueous solution. The membrane inlet probe was a 1.0-cm segment of Silastic tubing attached to the vacuum inlet leading to the ion source. Silastic is a semipermeable silicon rubber that allows flux of uncharged substances including nitric oxide (NO). The use of such an inlet to measure NO has several advantages that we demonstrate in this report. It provides a direct, continuous, and quantitative determination of dissolved nitric oxide concentrations over long periods of real time. The use of such an inlet in our system had a response time of 5 to 7 s and a detection lower limit with the current model of 1.0 nM. This apparatus was used to measure the generation of NO from solutions of nitrite, NONOates, and nitroprusside. The usefulness of such an inlet in measuring NO in physiological systems is discussed. 相似文献
36.
Baart GJ Zomer B de Haan A van der Pol LA Beuvery EC Tramper J Martens DE 《Genome biology》2007,8(7):R136
Background
Neisseria meningitidis is a human pathogen that can infect diverse sites within the human host. The major diseases caused by N. meningitidis are responsible for death and disability, especially in young infants. In general, most of the recent work on N. meningitidis focuses on potential antigens and their functions, immunogenicity, and pathogenicity mechanisms. Very little work has been carried out on Neisseria primary metabolism over the past 25 years. 相似文献37.
38.
Background
Representation of independent biophysical sources using Fourier analysis can be inefficient because the basis is sinusoidal and general. When complex fractionated atrial electrograms (CFAE) are acquired during atrial fibrillation (AF), the electrogram morphology depends on the mix of distinct nonsinusoidal generators. Identification of these generators using efficient methods of representation and comparison would be useful for targeting catheter ablation sites to prevent arrhythmia reinduction.Method
A data-driven basis and transform is described which utilizes the ensemble average of signal segments to identify and distinguish CFAE morphologic components and frequencies. Calculation of the dominant frequency (DF) of actual CFAE, and identification of simulated independent generator frequencies and morphologies embedded in CFAE, is done using a total of 216 recordings from 10 paroxysmal and 10 persistent AF patients. The transform is tested versus Fourier analysis to detect spectral components in the presence of phase noise and interference. Correspondence is shown between ensemble basis vectors of highest power and corresponding synthetic drivers embedded in CFAE.Results
The ensemble basis is orthogonal, and efficient for representation of CFAE components as compared with Fourier analysis (p ≤ 0.002). When three synthetic drivers with additive phase noise and interference were decomposed, the top three peaks in the ensemble power spectrum corresponded to the driver frequencies more closely as compared with top Fourier power spectrum peaks (p ≤ 0.005). The synthesized drivers with phase noise and interference were extractable from their corresponding ensemble basis with a mean error of less than 10%.Conclusions
The new transform is able to efficiently identify CFAE features using DF calculation and by discerning morphologic differences. Unlike the Fourier transform method, it does not distort CFAE signals prior to analysis, and is relatively robust to jitter in periodic events. Thus the ensemble method can provide a useful alternative for quantitative characterization of CFAE during clinical study. 相似文献39.
40.
Pattengale ND Aberer AJ Swenson KM Stamatakis A Moret BM 《IEEE/ACM transactions on computational biology and bioinformatics / IEEE, ACM》2011,8(4):902-911
Many of the steps in phylogenetic reconstruction can be confounded by “rogue” taxa—taxa that cannot be placed with assurance anywhere within the tree, indeed, whose location within the tree varies with almost any choice of algorithm or parameters. Phylogenetic consensus methods, in particular, are known to suffer from this problem. In this paper, we provide a novel framework to define and identify rogue taxa. In this framework, we formulate a bicriterion optimization problem, the relative information criterion, that models the net increase in useful information present in the consensus tree when certain taxa are removed from the input data. We also provide an effective greedy heuristic to identify a subset of rogue taxa and use this heuristic in a series of experiments, with both pathological examples from the literature and a collection of large biological data sets. As the presence of rogue taxa in a set of bootstrap replicates can lead to deceivingly poor support values, we propose a procedure to recompute support values in light of the rogue taxa identified by our algorithm; applying this procedure to our biological data sets caused a large number of edges to move from “unsupported” to “supported” status, indicating that many existing phylogenies should be recomputed and reevaluated to reduce any inaccuracies introduced by rogue taxa. We also discuss the implementation issues encountered while integrating our algorithm into RAxML v7.2.7, particularly those dealing with scaling up the analyses. This integration enables practitioners to benefit from our algorithm in the analysis of very large data sets (up to 2,500 taxa and 10,000 trees, although we present the results of even larger analyses). 相似文献